What country entered the Revolutionary War as a French ally in 1779?

The country that joined the French at that time was Spain, who controlled the area of what is now Florida. The Iroquois were on the French side but were allies the entire war and not a "European country".

Spain will enter in 1779 as an ally of France. The following year, Britain will declare war on the Dutch who have been engaging in profitable trade with the French and Americans.